1. Technical Field
The present invention relates to an elevator system and, more particularly, to an indicator which communicates speed and direction of travel of an elevator car during a power outage or elevator system shutdown.
2. Background Art
The conventional elevator system typically includes an elevator car traveling in a hoistway, as well as machinery and components operating and controlling the system. The elevator car has a car doorway that cooperates with hoistway doorways located on each floor of the building. The elevator car is suspended in the hoistway from a plurality of ropes driven by a motor.
The elevator car typically stops in the hoistway during a power failure or elevator system shut-down. In such event, there are usually procedures in place to rescue passengers who may be stranded in the elevator car when it stops in the hoistway. The first task for emergency workers is determining the location of the stranded elevator car in the hoistway. Depending on the elevator system, the elevator car may be found by connecting a handheld electronic display module to the control system which monitors the elevator system, or by physically observing the elevator machinery which can indicate the car location.
Once the location of the elevator car is established, emergency workers typically use gravity to raise or lower the elevator car to the nearest or safest floor. The combined weight of the elevator car and passengers determines the direction of travel: if the weight of the elevator car and passengers is more than that of the elevator counterweight, gravity will pull the elevator car downward; if it is less, gravity will move the car upward. An emergency brake is used to slowly raise or lower the elevator car. However, once the emergency brake is released, there may still be difficulties in determining the speed and direction of travel of the elevator car.
One elevator system provides a window into the hoistway to view the machinery, which has mechanical indicators to inform workers of elevator car movement. There are problems with this type of elevator system because installing the viewing window makes compliance with building codes more difficult. Additionally, the viewing window is usually located in an area that presents fire safety concerns. Also, if the elevator system has complex machinery, workers may require training to effectively correlate movement of machinery to a speed and travel direction of the elevator car.
Another solution for determining the speed and direction of travel of the elevator car is to use a back-up power supply to energize the electronics which control the elevator system under normal operating conditions. If the main power fails, the back-up power supply energizes the control system to provide movement information to the operators. In this type of system, back-up power may be useless if one of the electronic components fails and causes a system shut-down.
Therefore, there is a need for an elevator system that does not rely on a back-up power supply or problematic viewing windows to communicate the elevator car speed and direction of travel during emergency situations.